The present invention relates to apparatus and processes for automatic machine milking, providing for a plurality of milking phases with variable milking characteristics, each phase of which can be of a duration responsive to milk flow and time.
Machine milking, as known in the art, generally utilizes teat cups and vacuum sources to perform the milking function. In such prior art systems each teat is contained within a teat cup having a teat receiving liner, inside the cup next to the teat. A working vacuum is applied through each teat cup liner to draw the milk from the teat, with the teat liners periodically opened and collapsed by applications of a massage vacuum between the liner and the inside of the cup. This periodic working of the teat liners results in the periodic flow of milk from each teat into a milk line, and constitutes the actual milking of the cow.
Prior art milking machines have generally tended to perform under an unvarying milking condition throughout the milking processes, subjecting the teats to a constant level of working vacuum and to an unvarying pulsation of the teat liners. Such an unvarying milking condition can be undesirable, both in terms of the safety for the animal being milked and in terms of the quantity and quality of the milk obtained. Specifically, it is known that prior to milking, a cow must be adequately prepared to trigger the cow's let-down relexes and cause the cow to release her milk. If the teats are subjected to too high a level of working vacuum prior to the release of the cow's milk, the full vacuum acting upon the teat with no milk flow can injure the teat and may cause the cow discomfort, decreasing her milk production. Similarly, the risk of injury is great if the teats are subjected to the working vacuum after milk flow has ceased. To avoid some of these problems, users of such prior art machines generally prepare the cow for milking by manual stimulation of the cow's teats. After adequate preparation, teat cups are applied and the cow can be milked with decreased chance of injury or discomfort to the cow. After milk flow ceases, the working vacuum must be manually terminated to avoid injury.
Some prior art milking machines have incorporated apparatus enabling machine preparation of the cow for milking, and automatic termination after milking. For example U.S. Pat. No. 3,754,532, issued Aug. 28, 1973, discloses apparatus for subjecting the teats to a relatively low working vacuum and a relatively low frequency and low level of massage vacuum for machine stimulation of the cow, thereby rendering manual stimulation unnecessary. The apparatus of that patent also monitors the rate of flow of the milk obtained, and, upon attainment of a predetermined rate of milk flow, switches the apparatus to a second phase, subjecting the teats to a higher working vacuum and to a higher frequency and level of massage vacuum for the actual milking of the cow. When the rate of milk flow decreases at the end of this milking phase, the apparatus of the patent switches to a phase which subjects the teats to the relatively low working vacuum and relatively low frequency and low level of massage vacuum until the operator turns the machine off and removes the teat cups.
Other prior art apparatus provide for automatic removal of the teat cups when the milk flow ceases at the end of the milking phase, detecting the cessation of the milk flow by a milk flow indicator and then causing the teat cups to fall by removing the vacuums from the teat cups. Other arrangements catch the teat cups and remove them from the cow. See German Pat. No. 1,278,166, and U.S. Pat. No. 2,496,307, issued Feb. 7, 1950, and U.S. Pat. No. 3,246,631, issued Apr. 19, 1966.
Prior art milking machines generally milk all the teats simultaneously, with all the teat liners being pulsated concurrently. It has been found that several advantages can be obtained over this concurrent pulsation through the use of sequential pulsation, in which the teat liners are pulsed one after the other. This sequential pulsation results in even milk flow in the milk line, minimizes the risk of carrying over infection, suppresses air mixing in the milk, lowers free fatty acids in the milk, and controls the rancidity of the milk.
As seen above, some prior art systems have utilized a rate of milk flow indicator for varying the vacuums and rates of pulsation in response to an increase or decrease in rate of milk flow. While these systems do represent advances in milking efficiency and safety, it has been found that even greater efficiencies and safety can be achieved by looking at both the rate of milk flow and the lapse of time in certain situations, or in looking at either where appropriate. For example, it has been found that it is best to switch the system from the stimulation phase to the milking phase when the rate of milk flow achieves a predetermined level. If, however, that rate of flow is not achieved after the lapse of a predetermined time, it is best to switch to the milking phase regardless for purposes of system efficiency.
As seen above, some prior art systems can automatically operate with shift phases, as in U.S. Pat. No. 3,754,532 which can shift between a low vacuum, slow pulsation phase and a high vacuum, high pulsation phase in in response to the rate of milk flow. It has been found that even greater efficiencies and safety can be achieved by a system operating with additional phases. Thus, a system according to the invention can operate in a first, stimulation phase with vacuums and pulsation rates appropriate to stimulate the cow; in a second, milking phase appropriate to milk the cow; in a third, post-milking phase appropriate to finish the milking; and in a fourth, shut-off phase appropriate after milking for the convenience of the operator.